The Zero-Carbon House: It’s Just Around the Corner

Photo: Christopher Barrett

Carbon-Free Chicago

The Windy City’s first net-zero-energy home employs a butterfly roof and other smart design ideas to help it unplug from the grid.

Homes are responsible for 23 percent of the energy used in the US and 18 percent of carbon emissions. In cities like Chicago, where the temperature can vary by 100 degrees, heating and cooling bills can be bank-breakers. But it doesn’t have to be this way. Five years ago, local architecture and urban-design firm Farr Associates was asked to solve the problem. The company built a 2,600-square-foot house that is now “very, very close” to generating all of its own power, architect Jonathan Boyer says. The owners and designers continue to tweak the tech, and he’s expecting net-zero energy use in the next year-end report. Here’s a look at how it works.

Photo: Christopher Barrett

Earth-Friendly Elements

Water RecyclingThe “upside-down” roof not only conceals extensive solar arrays, it captures rainwater for irrigating the garden’s native plants. Inside, an innovative system treats gray water from the washing machine with chlorine and ultraviolet light and uses it to flush the home’s dual-tank toilets.

Geothermal WellsThree hundred feet under the garden, three geothermal wells store warm water (heated in part by the rooftop panels) and circulate it to the house for heating and cooling. In summer, the closed- loop system functions as a heat-exchange system, chilling the house much as an air conditioner does.

Radiant HeatIn winter, warm water is pumped from the geothermal wells and circulated through tubing embedded in the home’s concrete floors. That’s enough to heat floors to about 55 or 60 degrees; air pumped from the wells then kicks room temperatures up to a comfy high-60s, low-70s range.

Thick WallsThe external walls sandwich insulation between two 8-inch-thick concrete layers that protect the interior from outside temperature fluctuations. On hot days, the concrete absorbs and retains heat, keeping rooms cool; at night it slowly releases that heat to maintain steady temps around the clock.

Ultra-Efficient WindowsGlass is great for letting in sunlight, but in cold weather it lets heat out. Three coats of glazing give these windows more than twice the thermal resistance of standard double-paned glass. Add in honeycombed shades for yet more heat retention.

Illustration: Riccardo Vecchio

Godfather of Green

Want to outfit your home with the edgiest in eco-tech? Just ask engineer Jerry Yudelson.

Green building and carbon-neutral living might seem like recent ideas, but engineer Jerry Yudelson has been in the environmentally friendly building business for 14 years. Today he directs a consulting firm in Tucson, Arizona, and his name is on a dozen books about green design. Before LEED certification (that’s Leadership in Energy and Environmental Design, to us non-pros) was a glimmer in any architect’s eye, Yudelson was pushing for solar houses. And he still is. He offers his thoughts on where the field is headed, what new tricks are cutting energy use, and which technological leaps may yet take green homes mainstream.

Wired: You can hardly think of a green house without imagining solar panels. How has solar changed in recent years?

Jerry Yudelson: You’re getting solar a lot cheaper now. And it’s being incorporated into roof shingles, so you can actually have solar-powered roofs without putting on separate panels. You’ve got to put a roof on anyway, so if you can effectively make the roof itself a solar collector, you get two for one.

Wired: Bill Gates recently called rooftop solar “cute.” He seemed to think it was a rich person’s toy.

Yudelson: Production housing is where it’s getting interesting. The big home builders are starting to put on 2- or 3-kilowatt systems as a standard feature, and it’s just part of the price of the house. There’s no add-on cost. That’s a real breakthrough.

Wired: What about the systems that really run a house, like heating and cooling?

Yudelson: The real key is the windows. There’s some revolutionary nanotechnology that’s about to go into the glass—different kinds of coatings that make them five to 10 times more energy-efficient than double-paned windows. These windows are as energy-efficient as walls.

Wired: Right now, most of a home’s energy is used to control temperature. You’re going to solve the problem with fancy insulation?

Yudelson: Most of the energy demand in new homes is going to come from appliances—not the structure of the house itself but all the stuff we put into it. So there’s going to be a whole generation of smart appliances—smart water heaters and more—that you can control on the web. You tell it what to do; it tells you what it’s doing. That’s going to come in the next five years, maybe sooner.

Wired: But will people actually care about how much juice their DVRs suck up?

Yudelson: When you make energy monitors standard in new construction—when you integrate them with a smart thermostat system—you can make them something people will want to use. You know the old saying: You can’t manage what you can’t measure. You’ve got to have good information, and you’ve got to have it in real time. If you do, you’ll be in much better shape to manage.

Wired: So, dream a little: Imagine everything you think is coming is actually here. What do you build into your ideal home?

Yudelson: Solar on the roof. More indigenous plants instead of lawns. Thirty or 40 percent less water use inside, packaged with a gray-water system for flushing toilets and a rainwater-harvesting system. And one other important thing: It’s going to be smaller.